What roles do larger small arms cartridges fill for infantry?

[Curly_]

This came up in a recent discussion I had with a friend over Discord, concerning a hypothetical near-peer conflict (particularly in an urban environment). My friend is of the belief that in such a conflict there isn't no reason to field any small arms (not just service rifles or light machine guns) in anything larger than something like 5.56 NATO, the rationale being that a.) you can carry more of it compared something like 6.5 Creedmoor or 7.62 NATO, b.) you're mostly going to be using it suppressing the enemy so that you can drop high explosives on their heads, and c.) since most combat takes place under 300 meters the extra range would be unnecessary. Is there any merit to this line of thinking? What cases can be made for using more powerful, longer ranged cartridges in SDMRs and (tripod or vehicle mounted) machine guns?

[LoooSeR]

   What "larger caliber small arms catridges" are we talking about? 7.62x51/7.62x54R? 0.50 BMG/12.7x108?

   If we look at current conflict in Syria, use of personal small arms (AKs, ARs) is rare. Most of killing is done with weapons that use explosives and fragmentation. 14.5 mm HMGs are frequently used for suppression at long ranges. In fact, such ranges could be considered as "normal" for firefights in Syria, 23 mm ZUs and 14.5mm ZPUs are very popular and thanks to technicals they are mobile enough to appear everywhere on the frontline. Most of the time enemies don't get close to each other (as evident by ANNA news reports when islamists were leaving villages without even getting into close range fight) and prefer keeping distance to have space to maneuver. 

   Keep in mind that in case of Syrian warfare we are talking about mostly open terrain.

   You can watch selection of videos by ANNA news (posting only one with Eng subs) and see that most of the time infantry is just "clearing" towns and villages without having much of serious firefights. Some of short range firefights are happening against small groups of militants. That is probably one of several reasons why SAA is able to advance against enemies, while having pretty bad infantry (with exceptions).

   

Spoiler

 

 

 

[Sturgeon]

20 hours ago, Curly_ said:

This came up in a recent discussion I had with a friend over Discord, concerning a hypothetical near-peer conflict (particularly in an urban environment). My friend is of the belief that in such a conflict there isn't no reason to field any small arms (not just service rifles or light machine guns) in anything larger than something like 5.56 NATO, the rationale being that a.) you can carry more of it compared something like 6.5 Creedmoor or 7.62 NATO, b.) you're mostly going to be using it suppressing the enemy so that you can drop high explosives on their heads, and c.) since most combat takes place under 300 meters the extra range would be unnecessary. Is there any merit to this line of thinking? What cases can be made for using more powerful, longer ranged cartridges in SDMRs and (tripod or vehicle mounted) machine guns?

 

Your friend's scope is a little limited to be making calls like that. As an analogy, particularly if they are more "big boy" weapons oriented, even though most targets are destroyed by small missiles like Hellfire, that does not make Tomohawks useless or not worth keeping in inventory.

Also, "most combat takes place under 300 meters" is being applied too broadly here. The distances at which combat takes place varies greatly from conflict to conflict, for example, for the Americans, most combat in Syria has taken place at distances well over a kilometer, because it has been conducted primarily by aircraft and artillery. So while for infantry combat exclusively, yes that is true, it is not true for warfare overall, nor is it true in every case.

Making sense of larger caliber rounds can, somewhat reductively I admit, be done by looking at where they are used. If, by "infantry combat", you mean exclusively light infantry companies, then no, the .50 BMG round is not necessary, nor present at all in the light infantry platoon. However, do we include mechanized infantry, or cavalry dismounts in this? They have access to, and support from, anywhere from 30x113B, 25x137mm, or even 30x173mm with Stryker Dragoon. Do they need those rounds? Wrong question. Do those rounds benefit them and assist them in their mission? Absolutely.

It's wrong to say there's "no reason" to field, well, virtually any round. There are many reasons to field, for example, the .338 round so many companies and commentators are hot on right now, despite the fact that I think it would end up being a net negative in the end and get left at home almost all the time, in practice. So the question isn't about what reasons one can invent, but rather about whether the end result is an overall significant increase in force multiplication, and that has not only to do with the caliber being discussed but also its application.

[Lord_James]

Conversely, if you’re looking for something more empirical to base your judgments on, you can calculate the energy each bullet has within that range; more energy would imply more penetration for dealing with body armors and punching through make-shift fortifications like stone/concrete, though this is not always the case. 

[Beer]

After the terror attacks in Paris the French GIGN units ordered ČZ-806 in 7.62x39 to replace the 5.56x45 weapons. We can see that FSB units in Russia frequently use 9x39 weapons and it looks like they start using even 12.7x55 round for urban fighting. These units typically fight on very short distance with enemies often barricaded or equipped with ballistic vests. Hence why I would agree that there is a good reason why larger infantry calibers exists and it's up to the user to use them effectively. 

[LoooSeR]

1 hour ago, Beer said:

After the terror attacks in Paris the French GIGN units ordered ČZ-806 in 7.62x39 to replace the 5.56x45 weapons. We can see that FSB units in Russia frequently use 9x39 weapons and it looks like they start using even 12.7x55 round for urban fighting. These units typically fight on very short distance with enemies often barricaded or equipped with ballistic vests. Hence why I would agree that there is a good reason why larger infantry calibers exists and it's up to the user to use them effectively. 

   12.7x55 is almost never used (or never used at all). It is very rare catridge in units and both weapons in this caliber suck ass. Shorter versions of AK in both 5.45 and 7.62x39 are used most of the time.

[Sturgeon]

8 hours ago, Lord_James said:

Conversely, if you’re looking for something more empirical to base your judgments on, you can calculate the energy each bullet has within that range; more energy would imply more penetration for dealing with body armors and punching through make-shift fortifications like stone/concrete, though this is not always the case. 

 

This isn't really true. For example, the 6x45mm SAW had greater penetration than 7.62 NATO, despite having about 2/3rds the energy at range.

[Sturgeon]

3 hours ago, Beer said:

After the terror attacks in Paris the French GIGN units ordered ČZ-806 in 7.62x39 to replace the 5.56x45 weapons. We can see that FSB units in Russia frequently use 9x39 weapons and it looks like they start using even 12.7x55 round for urban fighting. These units typically fight on very short distance with enemies often barricaded or equipped with ballistic vests. Hence why I would agree that there is a good reason why larger infantry calibers exists and it's up to the user to use them effectively. 

Yeah but let's be honest the GIGN ordering 7.62x39 806s is just IRL memes.

[Curly_]

8 hours ago, Lord_James said:

Conversely, if you’re looking for something more empirical to base your judgments on, you can calculate the energy each bullet has within that range; more energy would imply more penetration for dealing with body armors and punching through make-shift fortifications like stone/concrete, though this is not always the case. 

That's pretty similar to my thoughts on the subject, though I look at things more in terms of supersonic range and sectional density (as well the capacity to use special effects rounds like the Mk 211 Raufoss). Theoretically one could make a .224-caliber cartridge with that matched the external ballistics and sectional density of a 140-grain 6.5 Creedmoor (which according to my math should be about 100 grains), but the projectile would end up being too far long for a standard ball loading, especially if it has to be lead-free.

[Sturgeon]

Just now, Curly_ said:

That's pretty similar to my thoughts on the subject, though I look at things more in terms of supersonic range and sectional density (as well the capacity to use special effects rounds like the Mk 211 Raufoss). Theoretically one could make a .224-caliber cartridge with that matched the external ballistics and sectional density of a 140-grain 6.5 Creedmoor (which according to my math should be about 100 grains), but the projectile would end up being too far long for a standard ball loading, especially if it has to be lead-free.

Bullet doesn't have to be that heavy, but I'm a weirdo .224 cal crackpot. 80 grains would do it.
 

I'm a little lukewarm on 6.5 Creedmoor as a 7.62 replacement specifically because of the limited bullet volume, but it really depends exactly what you planned to use. I personally think US forces are arguably missing out by not having any small (<.50) caliber API, but opinions differ.

[Sturgeon]

Like, here's an example worth thinking about: A 2-ton truck with layers of makeshift steel and concrete armor headed towards a checkpoint (AVBIED) at 60 mph. Will 5.56 penetrate that target, stopping it before it kills people at the checkpoint? No. Will 7.62? No. Will a TOW? If it hits, maybe, but the rate of fire is slow and you have little time. Will a 40mm AGL? Yes but not necessarily quickly and as it gets close you start entering your own danger space.

Will an M2A1, DShK, or KPV? Yeah, maybe!

[Beer]

You can't omit the economial side of the game. Sure there are better ammunition types available BUT you have to buy tenths of thousands of new weapons and billions of new bullets and scrape huge stock you have and which cost you fortune to buy some time a go. Hence why more special types of ammo are used basically only in limited number of specialized units. 

[Sturgeon]

Just now, Beer said:

You can't omit the economial side of the game. Sure there are better ammunition types available BUT you have to buy tenths of thousands of new weapons and billions of new bullets and scrape huge stock you have and which cost you fortune to buy some time a go. Hence why more special types of ammo are used basically only in limited number of specialized units. 

If only we had something roughly 12mm in caliber with loads of existing guns and ammunition laying around to support it. 

[Beer]

2 minutes ago, Sturgeon said:

If only we had something roughly 12mm in caliber with loads of existing guns and ammunition laying around to support it. 

 

I guess you mean Browning M2... 

[Sturgeon]

1 minute ago, Beer said:

 

I guess you mean Browning M2... 

 

that roughly 12mm caliber thing which we have oodles and oddles laying around yes.

[Sturgeon]

Related, some time ago I worked the math on penetrating a standard Jersey F barrier, and found you need 14.5x114 API to reliably go through.

[Curly_]

4 minutes ago, Sturgeon said:

Bullet doesn't have to be that heavy, but I'm a weirdo .224 cal crackpot. 80 grains would do it.
 

I'm a little lukewarm on 6.5 Creedmoor as a 7.62 replacement specifically because of the limited bullet volume, but it really depends exactly what you planned to use. I personally think US forces are arguably missing out by not having any small (<.50) caliber API, but opinions differ.

I'm pretty big into SCHV rounds myself. Running a 60 grain 5.45×39 at 2,900 ft/s though the JBM ballistics calculator was a real enlightening experience, seeing as it managed to meet, if not outright exceed, M80 ball's ballistics.

 

Also, what would be a better theoretical replacement for 7.62 NATO, in your opinion?

[Sturgeon]

1 minute ago, Curly_ said:

I'm pretty big into SCHV rounds myself.

 

I'm willing to bet you've read a few of my articles...
 

1 minute ago, Curly_ said:

Running a 60 grain 5.45×39 at 2,900 ft/s though the JBM ballistics calculator was a real enlightening experience, seeing as it managed to meet, if not outright exceed, M80 ball's ballistics.

 

In terms of drop and drift? Yeah, depends on your i7 FF but sure. Energy? Probably not.
 

2 minutes ago, Curly_ said:

Also, what would be a better theoretical replacement for 7.62 NATO, in your opinion?

 

6.8 GP won't be the worst thing for that.

[Curly_]

5 minutes ago, Sturgeon said:

I'm willing to bet you've read a few of my articles...

I have, actually. Pretty informative stuff.

 

8 minutes ago, Sturgeon said:

In terms of drop and drift? Yeah, depends on your i7 FF but sure. Energy? Probably not.

The i7 FF was the same as 7N6, which is .929 if Wikipedia is to be trusted. I figured that you'd be able to bump up the weight by making the core a bit like M855A1's (copper slug, steel penetrator) since military 5.45 typically uses a steel penetrator core. Some messing around in Fusion 360 helped confirm that for me. As far as the ballistics go, yeah, the energy is definitely not going to be the same. (Also, I must've misremembered the original velocity I ran it at, it was actually 2,920 ft/s. Still, good stuff.)

 

Spoiler

 

[Lord_James]

1 hour ago, Sturgeon said:

 

This isn't really true. For example, the 6x45mm SAW had greater penetration than 7.62 NATO, despite having about 2/3rds the energy at range.

I guess I should have specified that the bullets were of similar construction, and proportionally scaled to each other, but yes, bullet anatomy is just as important as its striking energy. 

[Sturgeon]

12 minutes ago, Curly_ said:

I have, actually. Pretty informative stuff.

 

The i7 FF was the same as 7N6, which is .929 if Wikipedia is to be trusted. I figured that you'd be able to bump up the weight by making the core a bit like M855A1's (copper slug, steel penetrator) since military 5.45 typically uses a steel penetrator core. Some messing around in Fusion 360 helped confirm that for me. As far as the ballistics go, yeah, the energy is definitely not going to be the same. (Also, I must've misremembered the original velocity I ran it at, it was actually 2,920 ft/s. Still, good stuff.)

 

  Hide contents

 

 

60gr is about right for an EPR for 5.45. I've designed a few of them, they're always promising. My latest bullet designs are even more efficient. Glad you enjoyed the articles; I've been surprised to find that Romulan v. Vulcan in particular seems to have been very influential to internet people.

[Sturgeon]

13 minutes ago, Lord_James said:

I guess I should have specified that the bullets were of similar construction, and proportionally scaled to each other, but yes, bullet anatomy is just as important as its striking energy. 

 Yes that's by and large true.

[tastethecake]

On 3/9/2020 at 5:33 PM, Sturgeon said:

Do they need those rounds? Wrong question. Do those rounds benefit them and assist them in their mission? Absolutely.

I am sure that they do indeed benefit greatly from those larger calibers. However the question I really am interested in is "Is it worth the production time and effort in a total war scenario". I also probably should scale down the scope for adopting a 5.56 like cartridge for all of the infantry to just squad level weapons, since mechanized formations need the punch of larger caliber weapons for anti vehicle purposes. However, this concept of mine is a little bit stupid now that I investigate it on a deeper level, it probably is just some mental backlash to the 6.8/7.62 rifle pain train the US military is going through right now.

TLDR: You guys have convinced me that this sorta idea makes no sense.

Edited March 12, 2020 by tastethecake
added a TLDR

[Sturgeon]

5 hours ago, tastethecake said:

I am sure that they do indeed benefit greatly from those larger calibers. However the question I really am interested in is "Is it worth the production time and effort in a total war scenario". I also probably should scale down the scope for adopting a 5.56 like cartridge for all of the infantry to just squad level weapons, since mechanized formations need the punch of larger caliber weapons for anti vehicle purposes. However, this concept of mine is a little bit stupid now that I investigate it on a deeper level, it probably is just some mental backlash to the 6.8/7.62 rifle pain train the US military is going through right now.

TLDR: You guys have convinced me that this sorta idea makes no sense.

For the rifle squad? Belt feds of any kind are haram. Everyone should be armed with the same weapon chambered for whatever your standard rifle caliber is. So it is written. So it will be done.

[Gripen287]

1 hour ago, Sturgeon said:

For the rifle squad? Belt feds of any kind are haram. Everyone should be armed with the same weapon chambered for whatever your standard rifle caliber is. So it is written. So it will be done.

 

A little off topic, and something I've tried to bring up in another thread, but before we go about haraming all belt-fed SAWs, I think there is at least one part of the belt-fed design space that could use a little more exploration, i.e., something inspired by the HK21/23, OTS-128, or Czech URZ with quick change "belt-mags."  Maybe throw in a little XM248 DNA too.  The HK21/23 proves that belt-fed levels of suppressive fire and a useful semi-automatic capability are not mutually exclusive if firing from a closed bolt.  The HK21 also easily integrates variable-power optics (and potentially clip-on night sights with an extended rail/mount).  Secret squirrel types value the HK21E for these reasons. 

 

If I were Sheikh for a day, I'd declare spare barrels haram within the rifle squad since the squad can't carry enough ammo to the point that they're required anyway.  I would however retain one or two belt-fed SAWs, chambered in the standard rifle caliber, within the rifle squad.  If chambered in 5.56 or 5.45, the SAW gunner probably gets two 200 round "belt-mags" for when close ambushes are likely and for covering the guys trying to throw grenades into a defensive position, but otherwise, the SAW gunner mostly fires on semi-auto from 60-100 round "belt-mags."  The old "belt-mag" would retain that pesky empty link from the expended belt, and the new "belt-mag" would present the first round in feed position, so the SAW gunner can just extract the old one, retain it (or not), and insert a new one, including at night and while moving.  Conceptually, the "belt-mag" is like attaching the HK21 feed mechanism and feed tray cover to each ammo box/drum and rocking the whole thing in like an AK drum. 

 

I've always been intrigued by these inverted belt feed systems, but I've never been able to find much information on the OTS-128 or URZ.  There doesn't seem to be much out there on the XM248 either, apart from the Weaponsman series, a few patents, and the technical manual.  Any idea why these inverted belt feed systems haven't received more attention?